The present invention relates to a medium voltage switchgear with improved features, and in particular to a medium voltage switchgear having a circuit breaker in the so-called withdrawable configuration. For the purposes of the present application the term medium voltage is referred to applications in the range from 1 kV up to some tens of KV, for example 52 kV.
With reference to FIG. 1, a medium voltage switchgear 1 is well known in the art and it usually consists of a casing 2 which defines an internal volume 3 for housing a circuit breaker assembly 4 and, e.g., a bus-bar assembly 39, as well as other systems, such as a feeder system and possible auxiliary equipment.
The circuit breaker assembly 4 is normally positioned inside a circuit breaker compartment, said circuit breaker assembly 4 being, in the so-called withdrawable configuration, movable between a service position, in which it is connected to the bus-bar and feeder systems, and a test/disconnected position in which it is isolated from the bus-bar and feeder systems. Depending on the application a grounding position is also possible.
In practice, with reference to FIG. 1 the circuit breaker assembly 4 can be moved from the service position shown in said figure, to a test/disconnected position and/or a grounding position, by sliding said assembly 4 toward the right-hand side of the figure. In order to do that, the circuit breaker assembly 4 is normally positioned on a sliding frame (not-shown) actuated from the outside of the casing 2. The sliding frame and its operation are well known in the art and will not be described in details here. In order to carry out the moving operation of the circuit breaker, an opening 5 is normally present of the front panel 21 of the switchgear 1, so as to allow the insertion and extraction of an operating handle.
A first drawback of the known solutions is due to the fact that the opening 5 allows a direct communication between the circuit breaker compartment and the outside of the switchgear 1, with safety concerns in case of faults, such as an internal arc.
Also, when the operating handle is inserted and the opening 5 is therefore closed (i.e. no direct communication between the inside and outside of the switchgear), a sudden increase of pressure inside the switchgear due to an internal fault may abruptly push away the handle with consequent safety concerns.